The present invention relates to the construction of a boot sole, and more particularly pertains to a new and improved safety boot sole construction to prevent puncturing of the sole by high energy and high velocity projectiles thus affording greater protection to an individual""s foot without over-restricting movement.
U.S. Pat. No. 5,237,758 to Zachman discloses semi-elliptical sections intersecting at loops with adjacent webs of adjacent loops intersecting with flexible rods directed through the intersecting loops to minimize lateral displacement of adjacent webs.
U.S. Pat. No. 5,285,583 to Aleven discloses a protective layer composed of plastic and including a flexible forepart portion having an insole board bonded to its bottom surface and a fabric liner bonded to its top surface during the process of moulding the protective plastic layer. The plastic used by Aleven is molten plastic injected in the final bonding process.
International Patent DE 4214802, by ZEPF H, to SPORTARTIKELFABRIK UHL GMBH KARL discloses a multi-layer boot sole having a walking surface, a damping intermediate sole, and an upper insole. The base is a thermo-plastic moulding, or is made of metal, ceramic, or graphite, in which multi-filament organic or inorganic reinforcing fibres are embedded in the form of a mat, or woven or knitted into the structure. The elastic profiled portions are formed on the underside of the base by injection moulding or pressing. The base can contain only a single layer of woven fibres, its total thickness being approximately 0.5 mm.
Aleven achieved strength and impact resistance from a plastic plate in the sole, and the use of a fabric mesh was to reinforce the plastic and not to provide impact resistance. ZLPF H could only achieve a single layer of not more than 0.5 mm thickness of woven fibres through injection moulding or pressing. Aleven made no discussion of metal, ceramic, or graphite materials. So far, techniques to use aramid, ceramic, or graphite fibres in the construction of a boot sole in thickness to prevent puncturing of the sole by high energy and high velocity projectiles has not been mentioned or made feasible due to problems in rigidity and bonding.
The boot soles described in the prior art are insufficient against blast and projectile protection when it is desired to conserve toe-to-heel flexion in order to enable running, jumping, rope climbing, and to clear obstacles such as rope ladders and small steps, and with sufficient feel or sensitivity to detect edges, pits, and small stones. To attain this, the present invention provides a blast and fragment resistant polyester and/or polyether-based polyurethane boot sole comprising embedded protective material in which the material is embedded throughout the entire sole and is composed of at least one woven polyaramid (Kevlar) layer, the denisity of which is less than or equal to 15 oz per square yard. Increasing density and additional layers of woven polyaramid fibres increases the blast and fragment resistance.
It is also an object of the present invention to provide a boot sole with good adhesion between the various polyaramid (Kevlar) layers and/or graphite fibre bundles in spite of the poor intrinsic adhesion between the polyaramid fibres, graphite fibres, and the polyurethane. Due to the extremely thin coating of the various polyaramid (Kevlar) and/or graphite fibre bundles prior to weaving and/or due to the relatively loose or coarse weave of the polyaramid (Kevlar) fibres, the polyurethane is able to penetrate between the fibres, allowing the various layers to be well bonded together, thereby preventing the peeling apart of the sole in subsequent use.
Accordingly to the invention, polyaramid (Kevlar) and/or graphite fibres can be coated thinly with polyester or polyether-based polyurethane before they are woven into the required mat form. This will greatly improve adhesion between the polyaramid and polyurethane material .
Also according to the invention, polyester fibres, preferably poly(ethylene terephthalate) (PET) fibres, can be interwoven with or between the (coated or uncoated) polyaramid (Kevlar) fibres to improve adhesion between the polyaramid and polyurethane material.
Also according to the invention, carbon graphite fibres can be interwoven with or between the polyaramid (Kevlar) layers to further strengthen and to stiffen the sole.
Also according to the invention, a woven layer of mineral fibres, notably ceramic fibres or S-Glass fibres, can be included into the boot sole to act as a fire wall for protection against hot gasses with temperatures of between 815 and 1,650 degrees Celsius.